// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// http://code.google.com/p/protobuf-j2me/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package com.google.protobuf;

import java.io.ByteArrayInputStream;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;

/**
 * Immutable array of bytes.
 * 
 * @author crazybob@google.com Bob Lee
 * @author kenton@google.com Kenton Varda
 */
public final class ByteString {
  private final byte[] bytes;

  protected ByteString(final byte[] bytes) {
    this.bytes = bytes;
  }

  /**
   * Gets the byte at the given index.
   * 
   * @throws ArrayIndexOutOfBoundsException
   *           {@code index} is < 0 or >= size
   */
  public byte byteAt(final int index) {
    return bytes[index];
  }

  /**
   * Gets the number of bytes.
   */
  public int size() {
    return bytes.length;
  }

  /**
   * Returns {@code true} if the size is {@code 0}, {@code false} otherwise.
   */
  public boolean isEmpty() {
    return bytes.length == 0;
  }

  // =================================================================
  // byte[] -> ByteString

  /**
   * Empty ByteString.
   */
  public static final ByteString EMPTY = new ByteString(new byte[0]);

  /**
   * Copies the given bytes into a {@code ByteString}.
   */
  public static ByteString copyFrom(final byte[] bytes, final int offset,
      final int size) {
    final byte[] copy = new byte[size];
    System.arraycopy(bytes, offset, copy, 0, size);
    return new ByteString(copy);
  }

  /**
   * Copies the given bytes into a {@code ByteString}.
   */
  public static ByteString copyFrom(final byte[] bytes) {
    return copyFrom(bytes, 0, bytes.length);
  }

  /**
   * Encodes {@code text} into a sequence of bytes using the named charset and
   * returns the result as a {@code ByteString}.
   */
  public static ByteString copyFrom(final String text, final String charsetName)
      throws UnsupportedEncodingException {
    return new ByteString(text.getBytes(charsetName));
  }

  /**
   * Encodes {@code text} into a sequence of UTF-8 bytes and returns the result
   * as a {@code ByteString}.
   */
  public static ByteString copyFromUtf8(final String text) {
    try {
      return new ByteString(text.getBytes("UTF-8"));
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("UTF-8 not supported?");
    }
  }

  // =================================================================
  // ByteString -> byte[]

  /**
   * Copies bytes into a buffer at the given offset.
   * 
   * @param target
   *          buffer to copy into
   * @param offset
   *          in the target buffer
   */
  public void copyTo(final byte[] target, final int offset) {
    System.arraycopy(bytes, 0, target, offset, bytes.length);
  }

  /**
   * Copies bytes into a buffer.
   * 
   * @param target
   *          buffer to copy into
   * @param sourceOffset
   *          offset within these bytes
   * @param targetOffset
   *          offset within the target buffer
   * @param size
   *          number of bytes to copy
   */
  public void copyTo(final byte[] target, final int sourceOffset,
      final int targetOffset, final int size) {
    System.arraycopy(bytes, sourceOffset, target, targetOffset, size);
  }

  /**
   * Copies bytes to a {@code byte[]}.
   */
  public byte[] toByteArray() {
    final int size = bytes.length;
    final byte[] copy = new byte[size];
    System.arraycopy(bytes, 0, copy, 0, size);
    return copy;
  }

  /**
   * Constructs a new {@code String} by decoding the bytes using the specified
   * charset.
   */
  public String toString(final String charsetName)
      throws UnsupportedEncodingException {
    return new String(bytes, charsetName);
  }

  /**
   * Constructs a new {@code String} by decoding the bytes as UTF-8.
   */
  public String toStringUtf8() {
    try {
      return new String(bytes, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("UTF-8 not supported?");
    }
  }

  // =================================================================
  // equals() and hashCode()

  public boolean equals(final Object o) {
    if (o == this) {
      return true;
    }

    if (!(o instanceof ByteString)) {
      return false;
    }

    final ByteString other = (ByteString) o;
    final int size = bytes.length;
    if (size != other.bytes.length) {
      return false;
    }

    final byte[] thisBytes = bytes;
    final byte[] otherBytes = other.bytes;
    for (int i = 0; i < size; i++) {
      if (thisBytes[i] != otherBytes[i]) {
        return false;
      }
    }

    return true;
  }

  private volatile int hash = 0;

  public int hashCode() {
    int h = hash;

    if (h == 0) {
      final byte[] thisBytes = bytes;
      final int size = bytes.length;

      h = size;
      for (int i = 0; i < size; i++) {
        h = h * 31 + thisBytes[i];
      }
      if (h == 0) {
        h = 1;
      }

      hash = h;
    }

    return h;
  }

  // =================================================================
  // Input stream

  /**
   * Creates an {@code InputStream} which can be used to read the bytes.
   */
  public InputStream newInput() {
    return new ByteArrayInputStream(bytes);
  }

  /**
   * Creates a {@link CodedInputStream} which can be used to read the bytes.
   * Using this is more efficient than creating a {@link CodedInputStream}
   * wrapping the result of {@link #newInput()}.
   */
  public CodedInputStream newCodedInput() {
    // We trust CodedInputStream not to modify the bytes, or to give anyone
    // else access to them.
    return CodedInputStream.newInstance(bytes);
  }

  // =================================================================
  // Output stream

  // /**
  // * Creates a new {@link Output} with the given initial capacity.
  // */
  // public static Output newOutput(final int initialCapacity) {
  // return new Output(new ByteArrayOutputStream(initialCapacity));
  // }
  //
  // /**
  // * Creates a new {@link Output}.
  // */
  // public static Output newOutput() {
  // return newOutput(32);
  // }

  // /**
  // * Outputs to a {@code ByteString} instance. Call {@link #toByteString()}
  // to
  // * create the {@code ByteString} instance.
  // */
  // public static final class Output extends OutputStream {
  // private final ByteArrayOutputStream bout;
  //
  // /**
  // * Constructs a new output with the given initial capacity.
  // */
  // private Output(final ByteArrayOutputStream bout) {
  // super(bout);
  // this.bout = bout;
  // }
  //
  // /**
  // * Creates a {@code ByteString} instance from this {@code Output}.
  // */
  // public ByteString toByteString() {
  // final byte[] byteArray = bout.toByteArray();
  // return new ByteString(byteArray);
  // }
  // }

  // /**
  // * Constructs a new ByteString builder, which allows you to efficiently
  // * construct a {@code ByteString} by writing to a {@link
  // CodedOutputStream}.
  // * Using this is much more efficient than calling {@code newOutput()} and
  // * wrapping that in a {@code CodedOutputStream}.
  // *
  // * <p>
  // * This is package-private because it's a somewhat confusing interface.
  // * Users can call {@link Message#toByteString()} instead of calling this
  // * directly.
  // *
  // * @param size
  // * The target byte size of the {@code ByteString}. You must write
  // * exactly this many bytes before building the result.
  // */
  // static CodedBuilder newCodedBuilder(final int size) {
  // return new CodedBuilder(size);
  // }

  // /** See {@link ByteString#newCodedBuilder(int)}. */
  // static final class CodedBuilder {
  // private final CodedOutputStream output;
  // private final byte[] buffer;
  //
  // private CodedBuilder(final int size) {
  // buffer = new byte[size];
  // output = CodedOutputStream.newInstance(buffer);
  // }
  //
  // public ByteString build() {
  // output.checkNoSpaceLeft();
  //
  // // We can be confident that the CodedOutputStream will not modify
  // // the
  // // underlying bytes anymore because it already wrote all of them.
  // // So,
  // // no need to make a copy.
  // return new ByteString(buffer);
  // }
  //
  // public CodedOutputStream getCodedOutput() {
  // return output;
  // }
  // }

  /**
   * Helper called by generated code to construct default values for string
   * fields.
   * <p>
   * The protocol compiler does not actually contain a UTF-8 decoder -- it just
   * pushes UTF-8-encoded text around without touching it. The one place where
   * this presents a problem is when generating Java string literals. Unicode
   * characters in the string literal would normally need to be encoded using a
   * Unicode escape sequence, which would require decoding them. To get around
   * this, protoc instead embeds the UTF-8 bytes into the generated code and
   * leaves it to the runtime library to decode them.
   * <p>
   * It gets worse, though. If protoc just generated a byte array, like: new
   * byte[] {0x12, 0x34, 0x56, 0x78} Java actually generates *code* which
   * allocates an array and then fills in each value. This is much less
   * efficient than just embedding the bytes directly into the bytecode. To get
   * around this, we need another work-around. String literals are embedded
   * directly, so protoc actually generates a string literal corresponding to
   * the bytes. The easiest way to do this is to use the ISO-8859-1 character
   * set, which corresponds to the first 256 characters of the Unicode range.
   * Protoc can then use good old CEscape to generate the string.
   * <p>
   * So we have a string literal which represents a set of bytes which
   * represents another string. This function -- stringDefaultValue -- converts
   * from the generated string to the string we actually want. The generated
   * code calls this automatically.
   */
  public static String stringDefaultValue(String bytes) {
    try {
      return new String(bytes.getBytes("ISO-8859-1"), "UTF-8");
    } catch (UnsupportedEncodingException e) {
      // This should never happen since all JVMs are required to implement
      // both of the above character sets.
      throw new IllegalStateException("Standard character set not supported.");
    }
  }

  /**
   * Helper called by generated code to construct default values for bytes
   * fields.
   * <p>
   * This is a lot like {@link #stringDefaultValue}, but for bytes fields. In
   * this case we only need the second of the two hacks -- allowing us to embed
   * raw bytes as a string literal with ISO-8859-1 encoding.
   */
  public static ByteString bytesDefaultValue(String bytes) {
    try {
      return ByteString.copyFrom(bytes.getBytes("ISO-8859-1"));
    } catch (UnsupportedEncodingException e) {
      // This should never happen since all JVMs are required to implement
      // ISO-8859-1.
      throw new IllegalStateException("Standard character set not supported.");
    }
  }
}
